Sandy I. Helman

Learn More
To study and define the early time-dependent response (< or = 6 h) of blocker-sensitive epithelial Na+ channels (ENaCs) to stimulation of Na+ transport by aldosterone, we used a new modified method of blocker-induced noise analysis to determine the changes of single-channel current (iNa) channel open probability (Po), and channel density (NT) under(More)
Blocker-induced noise analysis and laser scanning confocal microscopy were used to test the idea that cAMP-mediated vesicle exocytosis/endocytosis may be a mechanism for regulation of functional epithelial Na+ channels (ENaCs) at apical membranes of A6 epithelia. After forskolin stimulation of Na+ transport and labeling apical membranes with the fluorescent(More)
Measurements of transepithelial electrical impedance of continuously short-circuited A6 epithelia were made at audio frequencies (0.244 Hz to 10.45 kHz) to investigate the time course and extent to which prostaglandin E(2) (PGE(2)) modulates Cl(-) transport and apical membrane capacitance in this cell-cultured model epithelium. Apical and basolateral(More)
Methods of blocker-induced noise analysis were used to investigate the way in which forskolin and vasopressin stimulate Na transport at apical membranes of short-circuited frog skin transporting Na at spontaneous rates of transport. Experiments were done under conditions where the apical Ringer solution contained either 100 mM Na or a reduced Na(More)
Activation of protein kinase C with phorbol 12-myristate 13-acetate (PMA) caused complex transient perturbations of amiloride-sensitive short-circuit Na+ currents (INa) in A6 epithelia and frog skins that were tissue and concentration dependent. A noninvasive channel blocker pulse method of noise analysis (18) was used to investigate how PMA caused(More)
Isolated epithelia of frog skin were prepared with collagenase, and the cells were punctured with intracellular microelectrodes across their apical (outer) and basolateral (inner) surfaces. Regardless of the route of cell puncture, the intracellular voltage (Vosc) in short-circuited isolated epithelia was markedly negative, averaging -70.4 mV for apical(More)
Epithelia of frog skin bathed either symmetrically with a sulfate-Ringer solution or bathed asymmetrically and depolarized with a 112 mM K+ basolateral solution (Kb+) were studied with intracellular microelectrode techniques. Kb+ depolarization caused an initial decrease of the short-circuit current (Isc) with a subsequent return of the Isc toward control(More)
The basolateral membrane of amphotericin-treated turtle colon can exhibit two distinct types of K+ conductance, one of which is associated with cell swelling and is blocked by quinidine or lidocaine. Fluctuations in basolateral K+ currents were analyzed under swelling (mucosal KCl) and nonswelling (mucosal K gluconate) conditions. Under nonswelling(More)
Noise analysis of the Na+ channels of the apical membranes of frog skin bathed symmetrically in a Cl-HCO3 Ringer solution was done with amiloride and CGS 4270. Tissues were studied in their control states and after inhibition of transepithelial Na+ transport (Isc) by addition of quinine or quinidine to the apical solution. A critical examination of the(More)
Blocker-induced noise analysis of apical membrane Na channels of epithelia of frog skin was carried out with the electroneutral blocker (CDPC, 6-chloro-3,5-diamino-pyrazine-2-carboxamide) that permitted determination of the changes of single-channel Na currents and channel densities with minimal inhibition of the macroscopic rates of Na transport(More)